The present invention relates generally to a safety syringe, and more particularly to an improved assembly of needle holder and barrel of the safety syringe.
The conventional safety syringe comprises a barrel and a needle holder which can be drawn into the barrel in the wake of injection, thanks to an engagement structure which is disposed between the barrel and the needle holder. However, the assembly of the barrel and the needle holder of the conventional safety syringe is defective in design in that the needle holder can be drawn into the barrel with a minimum effort, thereby resulting in user""s inconvenience as well as injection hazard.
It is the primary objective of the present invention to provide a syringe comprising a barrel and a needle holder which can be restrictively rotated within a range by a predetermined rotational force, so as to enhance the safety of the syringe.
It is another objective of the present invention to provide a syringe with an assembling structure for joining the barrel and the needle holder of the syringe without difficulty.
In keeping with the principle of the present invention, the foregoing objectives of the present invention are attained by a safety syringe comprising a barrel, a needle holder, and a plunger. The barrel has a receiving hole, a retaining block located in the inner edge of the receiving hole, an initial stop portion, a final stop portion, and a rotation resisting portion. The needle holder has a retaining groove, a stop rotation rod capable of turning between the initial stop portion and the final stop portion of the barrel, a overcoming portion capable of passing the rotation resisting portion at the time when the needle holder is turned by a predetermined force, and a catching turning cooperating portion located at the rear end. The plunger has a front rod body received in the receiving hole of the barrel, a catching turning portion disposed at the front end for retaining the catching turning cooperating portion of the needle holder.
When the plunger is not yet engaged with the needle holder, the overcoming portion of the needle holder is stopped at the rotation resisting portion of the barrel. As the plunger is engaged with the needle holder such that the needle holder is turned, the overcoming portion of the needle holder overcomes the rotation resisting portion of the barrel, thereby enabling the retaining groove of the needle holder to be opposite in location to the retaining block of the barrel. The needle holder can be thus drawn back in.